1. Field of the Invention
The invention relates to an AC brushless doubly-fed motor designed in accordance with slot harmonic magnetomotive force (MMF) of rotor windings. It belongs to the field of motor technology.
2. Description of the Related Art
AC brushless doubly-fed motors are applicable to frequency-conversion speed regulation systems, with reliable operation and low capacity of frequency converter. The motor stators are normally equipped with two sets of windings with pole pair number of p1 and p2, respectively. When the stator winding p1 connects to a power grid power supply, a rotating magnetic field is created with pole pair number of p1 Except p1 pairs of pole magnetic fields, p2 pairs of pole magnetic fields are also created by induced current in the rotor. In terms of the rotor, these two types of magnetic fields rotate in an opposite direction. If a variable-frequency power supply (VFPS) is connected with the stator winding p2, the rotational speed of the motor can be changed by means of changing the frequency of the VFPS.
Rotor plays a crucial role in brushless doubly-fed variable-frequency speed regulation motors. Conventional rotors mainly include reluctance rotors and cage rotors. Since the iron core of the reluctance rotor must be made into a salient structure and the windings of the cage rotor must be made into a concentric type short-circuited winding, the two rotors can only be used with specific number of poles. In addition, compare with conventional AC motor rotors, the above two rotors have a relatively larger volume and poor performance index.
AC brushless doubly-fed motors can also be used as electric generators, and for either wind or hydraulic power generation, they must be used under variable-speed constant-frequency power output conditions.